US7696471B2 - Impact detection system using an optical fiber sensor - Google Patents
Impact detection system using an optical fiber sensor Download PDFInfo
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- US7696471B2 US7696471B2 US11/987,533 US98753307A US7696471B2 US 7696471 B2 US7696471 B2 US 7696471B2 US 98753307 A US98753307 A US 98753307A US 7696471 B2 US7696471 B2 US 7696471B2
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- 238000001514 detection method Methods 0.000 title claims abstract description 48
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- 238000001228 spectrum Methods 0.000 claims description 33
- 230000002194 synthesizing effect Effects 0.000 claims description 4
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- 239000011521 glass Substances 0.000 claims description 2
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- 239000002131 composite material Substances 0.000 description 19
- 238000010586 diagram Methods 0.000 description 10
- 230000007423 decrease Effects 0.000 description 4
- 239000000835 fiber Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 239000004918 carbon fiber reinforced polymer Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/08—Testing mechanical properties
- G01M11/083—Testing mechanical properties by using an optical fiber in contact with the device under test [DUT]
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35303—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using a reference fibre, e.g. interferometric devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35383—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using multiple sensor devices using multiplexing techniques
- G01D5/35387—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using multiple sensor devices using multiplexing techniques using wavelength division multiplexing
Definitions
- the present invention relates to an impact detection system using an optical fiber sensor.
- CFRP carbon fiber reinforced plastic
- Japanese Patent Application Laid-Open Publication No. 2005-98921 describes a damage detecting apparatus using a fiber Bragg grating (FBG) optical fiber sensor.
- FBG fiber Bragg grating
- the invention described in the Japanese Patent Application Laid-Open Publication No. 2005-98921 detects the damage of a composite material on the basis of a change of the output of characteristic detecting means by vibrating the composite material with a piezo-element.
- the invention uses the following components for the detection of the damage: the piezo-element fixed to be disposed at a predetermined position of a composite material structure; a lead wire to transmit a signal to the piezo-element; the optical fiber sensor fixedly disposed so that the composite material constituting the composite material structure is put between the optical fiber sensor and the piezo-element, which sensor has a grating portion reflecting a light of a predetermined wavelength on a core portion; a light source performing the radiation of a light to a core portion; and the characteristic detecting means for detecting the characteristics of the reflected light from the grating portion.
- a spectrum analyzer or the like to detect the frequency characteristic of the reflected light from the grating portion is used as the characteristic detecting means.
- the invention described in the Japanese Patent Application Laid-Open Publication No. 2005-98921 cannot specify the existence, the position, and the magnitude of an impact having an arbitrary magnitude when an object structure receives the impact at an arbitrary position on the structure because the invention aims to detect a damage and the piezo-element is accordingly disposed at a predetermined position.
- the system loading a known vibration on the object structure by the piezo-element to detect the damage on the basis of the propagation result of the vibration cannot grasp all the changes from a change of a reflected light vibrating large to a change of a reflected light vibrating small, and cannot specify the existence, the position, and the magnitude of an arbitrary impact with high accuracy.
- an impact detection system comprising: an optical fiber including a core portion, the core portion including a plurality of sensor sections each provided with a grating portion, in which the grating portion is provided with a plurality of gratings each reflecting light, wavelength band of reflected light changes when a distance between the adjacent gratings changes, and the optical fiber vibrates the wavelength band depending on an elastic wave propagating through a subject to be inspected; a light source to input light into the core portions of the optical fiber, in which a spectrum bandwidth of the light includes vibration bands of the wavelength bands of the sensor sections; optical filters each connected to an output terminal of the optical fiber from which output terminal the reflected light is output; and an arithmetic processing unit to perform arithmetic processing of output values of the plurality of sensor sections through the optical filters, so as to detect the impact to the subject, wherein the wavelength bands of the sensor sections in the optical fiber are distributed to be apart from each other such that the vibration bands do not overlap with each other, and a
- FIG. 1 is a schematic configurational view of a basic impact detection system
- FIG. 2A is a schematic configurational view of an optical fiber sensor
- FIG. 2B is a diagram showing the changes of the refraction index of a grating portion in the traveling direction of a light
- FIG. 3A is a configurational diagram showing the optical fiber sensor and a spectrum analyzer connected to the sensor, and FIG. 3B is a spectrum diagram showing the pass bands of eight optical filters;
- FIG. 4A is a diagram showing the waveform of an input wave into the optical filter
- FIG. 4B is a spectrum diagram showing the pass band of two optical filters
- FIG. 4C is a diagram showing the waveforms of output waves of the optical filters
- FIG. 5A is a plan view showing an example of the arrangement of each optical fiber sensor in an embodiment of the present invention
- FIG. 5B is a spectrum diagram showing the pass bands of the optical filters corresponding to the arrangement of FIG. 5A and a wavelength distribution of a reflected light;
- FIG. 6 is a plan view showing another example of the arrangement of each optical fiber sensor in the embodiment of the present invention.
- FIG. 7 is a spectrum diagram showing the pass bands of the optical filters corresponding to the arrangement of FIG. 6 and a wavelength distribution of the distribution bands of reflected lights.
- FIG. 1 is a schematic configurational view of an impact detection system 10 to perform the detection of an impact to a composite material structure Z.
- the composite structure Z is used as a subject to be inspected.
- the impact detection system 10 of the present embodiment is equipped with optical fiber sensors (sensor sections) 30 installed at predetermined positions of the composite material structure Z, in which the detection of an impact 21 is to be performed, by being embedded or stuck; a spectrum analyzer 42 to detect the wavelength characteristics of reflected lights obtained from the optical fiber sensors 30 ; and an arithmetic processing apparatus 50 to performing the arithmetic processing of an output value of the spectrum analyzer 42 .
- a power supply device 43 of the spectrum analyzer 42 is shown.
- Each of the optical fiber sensors 30 is a fiber Bragg grating (FBG) optical fiber sensor. As shown in the schematic configurational view of FIG. 2A , each of the optical fiber sensors 30 includes a grating portion 33 reflecting a light of a predetermined wavelength in the core portion 32 of the optical fiber sensor 30 to be formed as an optical fiber 34 .
- FBG fiber Bragg grating
- the optical fiber 34 is connected to the spectrum analyzer 42 at one end of the optical fiber 34 , and irradiating lights covering the whole wavelength band of a predetermined range are entered into the core portion 32 by the light source provided in the spectrum analyzer 42 .
- the lights entering from the spectrum analyzer 42 propagate through the core portion 32 , and lights having only a part of wavelengths of the entering lights are reflected at the grating portion 33 .
- FIG. 2B is a diagram showing the changes of a refraction index of the core portion 32 in the traveling direction of a light, and a range L in the figure shows the refraction index in the grating portion 33 .
- the grating portion 33 is formed so as to change the refraction index of the core portion 32 at a fixed period.
- the grating portion 33 selectively reflects only the light having a specific wavelength at the boundary parts where the refraction index changes. If a disturbance, such as strain caused by a vibration, is applied to the grating portion 33 , then the grating intervals thereof change (expansion or contraction), and the wavelength of the reflected light thereby changes.
- the wavelength change ⁇ B of a reflected light of an FBG optical fiber sensor can be expressed here by the following formula, where n denotes the effective refractive index of the core, ⁇ denotes a grating interval, P 11 and P 12 denote Pockels coefficients, ⁇ denotes a Poisson ratio, ⁇ denotes applied strain, ⁇ denotes the temperature coefficient of the fiber material, and ⁇ T denotes a temperature change (see Alan D. Kersey, “Fiber Grating Sensors,” JOURNAL OF LIGHTWAVE TECHNOLOGY, Vol. 15, No. 8, 1997).
- ⁇ B 2 ⁇ n ⁇ ⁇ ⁇ ( ⁇ 1 - ( n 2 2 ) ⁇ [ P 12 - ⁇ ⁇ ( P 11 + P 12 ) ] ⁇ ⁇ ⁇ + [ ⁇ + ( d n d T ) n ] ⁇ ⁇ ⁇ ⁇ T ) Consequently, when a vibration propagates to the grating portion 33 , the strain amount ⁇ of the grating portion 33 changes, and the wavelength of a reflected light changes according to the strain amount ⁇ as a result. That is, the amount of change ⁇ B of a wave length changes according to the magnitude of a vibration applied to the grating portion 33 .
- FIG. 3A shows a configuration example of an optical fiber sensor and the spectrum analyzer 42 connected to it.
- the spectrum analyzer 42 includes a light source 61 , an optical circulator 62 , an arrayed waveguide grating (AWG) module 63 , and a photoelectric transducer 60 .
- the optical fiber 34 that is composed of four optical fiber sensors 30 a - 30 d that have different reflection wavelengths from one another and are connected in series is connected to the spectrum analyzer 42 .
- the minimum configuration three optical fiber sensors 30 are required.
- the light source 61 is a wide band light source including a vibration band of reflection wavelengths of the optical fiber sensors 30 a - 30 d .
- the reflection wavelength characteristic of an optical fiber sensor changes to the outside of the wavelength band of the light source, no reflected lights are produced. Consequently, the wavelength band of the light source limits the detection range of vibrations. It is preferable to set the light source to have a sufficiently wide band in order that a perfect reflected light is always emitted even if the reflection wavelengths of the optical fiber sensors 30 a - 30 d vibrate by an impact.
- the vibration band of the reflection wavelengths of an optical fiber sensor depends on the characteristics of the optical fiber sensor, an impact, the quality of the material of a subject to be inspected.
- the optical circulator 62 causes a light from the light source 61 to travel to the side of the sensor sections 30 a - 30 d of the optical fiber sensor 34 , and guides the reflected lights returned from the sensor sections 30 a - 30 d of the optical fiber sensor 34 to the input port P 0 of the AWG module 63 .
- the reflected light guided by the optical circulator 62 is introduced into the input port P 0 of the AWG module 63 by an optical fiber 69 .
- the AWG module 63 includes an AWG board 64 .
- a lightwave circuit monolithically integrated on a glass substrate by the technique of the optical waveguide is formed on the AWG board 64 .
- the lightwave circuit on the AWG board 64 includes input and output slab waveguides 65 and 66 , an arrayed waveguide 67 , and an output waveguide 68 , and constitutes eight optical filters that are connected to the input port P 0 in parallel with one another and have respectively different pass bands.
- the lightwave circuit on the AWG board 64 separates the multiplexed-wavelength input light, into the lights having respective wavelengths, by distributing the input light to pass it through the eight optical filters 59 , and outputs the lights in parallel with one another to eight output ports P 1 -P 8 .
- the number of the output ports in practical use is not limited to eight.
- the pass bands of the respective optical filters 59 corresponding to the eight output ports P 1 -P 8 are shown in the spectrum diagram of FIG. 3B .
- an optical filter 59 passes the reflected light corresponding to the part in which the reflected light input distribution 70 of the reflected light from the sensor section 30 b having a center wavelength ⁇ 2 in FIG. 38 overlaps with a pass band 71 of the optical filter, and outputs the passed reflected light to the output port P 3 .
- another optical filter 59 passes the reflected light corresponding to the part in which the reflected light overlaps with a pass band 72 , and outputs the passed reflected light to the output port P 4 .
- the optical filters 59 made to correspond to the one optical fiber sensor section 30 b are set as three optical filters or more.
- an input distribution 73 T of the reflected light from the sensor section 30 appears.
- an elastic wave from an impact position as a vibration source position propagates through the composite material structure Z, and the sensor section 30 vibrates the wavelength of the reflected light to be output therefrom according to the elastic wave propagating through the composite structure Z.
- the vibration of the wavelength is shown as an input wave 73 W of FIG. 4A .
- the reflected light input distribution 73 T shown in FIG. 4B shifts to a higher and lower level alternately to vibrate, and the value of the wavelength repeats increase and decrease.
- the higher optical filer passes the reflected light corresponding to the part where the reflected light input distribution 73 T overlaps with a pass band 75 T, and outputs the passed reflected light.
- the lower optical filter passes the reflected light corresponding to the part where the reflected light input distribution 73 T overlaps with the pass band 74 T, and outputs the passed reflected light.
- the spectrum analyzer 42 shown in FIG. 3A outputs light waves to the output ports P 1 -P 8 on the basis of the principle mentioned above, and the photoelectric transducer 60 converts the light waves into electric signals to output them to the outside.
- the outputs of the spectrum analyzer 42 receive the A/D conversion through a not shown interface, and are input into the arithmetic processing apparatus 50 .
- the arithmetic processing apparatus 50 performs the arithmetic processing for calculating the existence, the position, and the magnitude of an impact on the basis of the output values of the spectrum analyzer 42 . Moreover, the arithmetic processing apparatus 50 performs the recording of the operation results.
- the arithmetic processing apparatus 50 of the present embodiment is composed of an electronic computer.
- the arithmetic processing apparatus 50 is composed of, for example, a central processing unit (CPU) performing arithmetic processing in conformity with a program; a read only memory (ROM) storing the program; a random access memory (RAM) storing input value data from the spectrum analyzer 42 , and the data in the operation processes in conformity with a program and the data of operation results; an interface performing the transmission and the reception of data with spectrum analyzer 42 ; an image output interface converting the display data of the operation results into an image signal of a suitable format to output the converted image signal to a display monitor; and a data bus performing the transmission of various instructions and data among the respective components mentioned above.
- CPU central processing unit
- ROM read only memory
- RAM random access memory
- the impact detection system of the embodiment of the present invention is composed of an optical fiber including a plurality of FBG optical fiber sensors, a spectrum analyzer, an arithmetic processing unit to be configured as follows.
- the number of the optical filters corresponding to one optical fiber sensor is m (where m is an integer equal to 3 or more), and that the number of the optical fiber sensors to be used in one optical fiber is n (where n is an integer equal to 2 or more).
- a (m ⁇ n) channel AWG module is used as the AWG module to be configured in the spectrum analyzer. That is, (m ⁇ n) optical filters, which have different pass bands and are connected in parallel to the input port P 0 , are configured in the AWG module, and the AWG module includes (m ⁇ n) output ports (output channels) corresponding to the respective optical filters.
- one optical fiber in which 10 optical fiber sensors FBG 1 -FBG 10 are formed is drawn around, and the optical fiber sensors FBG 1 -FBG 10 (FBG 5 -FBG 10 are not shown) are thus installed in the composite material structure Z at intervals.
- the output terminal of the reflected light of the optical fiber is connected to the input port P 0 .
- the center wavelengths of the optical fiber sensors FBG 1 -FBG 10 are denoted by ⁇ 1 - ⁇ 10 , respectively.
- the wavelength bands R 1 -R 10 (R 5 -R 10 are not shown) of the respective optical fiber sensors FBG 1 -FBG 10 having the center wavelengths ⁇ 1 - ⁇ 10 , respectively, are distributed at regular intervals to be distant from each other to the degree or more at which the vibration bands of the detection objects are not overlapped with each other as shown in FIG. 5B .
- the pass bands (for example, F 1 -F 4 ) of the four optical filters corresponding to one optical fiber sensor are distributed in the vibration band, which is the detection object, of the corresponding optical fiber sensor at regular intervals over the center wavelength ( ⁇ 1 to F 1 -F 4 ) at the time of no impact loading on the corresponding one optical fiber sensor.
- one optical fiber in which 10 optical fiber sensors FBG 1 -FBG 10 are formed is drawn around, and the optical fiber sensors FBG 1 -FBG 10 (FBG 9 and FBG 10 are not shown) are thus installed in the composite material structure Z at intervals.
- the output terminal of the reflected light of the optical fiber is connected to the input port P 0 .
- the center wavelengths of the optical fiber sensors FBG 1 -FBG 10 are denoted by ⁇ 1 - ⁇ 10 , respectively.
- the wavelength bands R 1 -R 10 (R 9 and R 10 are not shown) of the respective optical fiber sensors FBG 1 -FBG 10 having the center wavelengths ⁇ 1 - ⁇ 10 , respectively, are distributed at regular intervals to be distant from each other to the degree or more at which the vibration bands of the detection objects are not overlapped with each other as shown in FIG. 7 .
- the pass bands (for example, F 1 -F 4 ) of the four optical filters corresponding to one optical fiber sensor are distributed in the vibration band, which is the detection object, of the corresponding optical fiber sensor at regular intervals over the center wavelength ( ⁇ 1 to F 1 -F 4 ) at the time of no impact loading on the corresponding one optical fiber sensor.
- the arithmetic processing unit stores the position coordinates of the optical fiber sensors FBG 1 -FBG 10 , and the center wavelengths ⁇ 1 - ⁇ 10 in association with each other.
- the vibration band of a detection object to be trapped of an optical fiber sensor the number m of the optical filters corresponding to one optical fiber sensor, and the distribution intervals of the optical filters are determined as follows, for example.
- the strain level in the generation of an impact damage that cannot be seen by eyes and causes a problem in an FRP composite material is in a range from about 300 ⁇ to about 500 ⁇ .
- the strain level of 1000 ⁇ of being about twice as large as the range as the maximum detectable strain it is necessary to trap the vibration band of 1.0 nm.
- the usage means to select m 6.
- the usage means to select m 3. It is a matter of course that the number m of the optical filters may be selected as 4 or 5, and may be selected as 7 or more. If the number m of the optical filters is set to be large, the detection of a change of a reflected light becomes higher accurate. On the other hand, the scale of the AWG module becomes large.
- the one having a band wider than the degree of including the vibration bands of the detection objects of all the optical fiber sensors to be used is used.
- wavelength vibrations having different amplitudes A 1 , A 2 , A 3 , A 4 , . . . are produced in the respective optical fiber sensors FBG 1 -FBG 10 as shown in FIG. 5B .
- the relative sizes of the amplitudes are as follows: A 1 >A 2 >A 3 >A 4 .
- wavelength vibrations having different amplitudes A 1 , A 2 , A 3 , A 4 , . . . are produced in the respective optical fiber sensors FBG 1 -FBG 10 as shown in FIG. 7 .
- all the output ports of the AWG module outputs output values including various kinds of information, such as the existence of an output, the nonexistence of any outputs, the existence of time changes of an output value, the nonexistence of any time changes of an output value, and further the situation of the time changes, to the arithmetic processing unit.
- the arithmetic processing unit can measure the energy levels of the elastic waves that have arrived at the respective optical fiber sensors FBG 1 -FBG 10 by synthesizing the output values of the AWG module obtained by such a way.
- the arithmetic processing unit calculates the existence of an impact, the position where the impact has bee applied, and the magnitude (energy level) of the impact, on the basis of these pieces of information.
- More optical fibers and more spectrum analyzers are installed according to the scale of the composite material structure Z, and are connected to the common arithmetic processing unit.
- one optical fiber in which a plurality of sensor sections is formed is used as a detection device; the wavelength bands of the respective sensor sections in the one optical fiber are distributed in the state of being respectively more distant to the degree at which any vibration bands do not overlap on each other; and the pass bands of three or more optical filters corresponding to one optical sensor are distributed in the vibration band of the corresponding one optical sensor over the center wavelength at the time of no impact loading to the corresponding one optical fiber sensor. Consequently, the changes of a reflected light from the one vibrating large to the one vibrating small are separated every sensor and are grasped by three or more filters. The changes are thereby correctly and sufficiently grasped, and the existence, the position, and the magnitude of an arbitrary impact can be specified with high accuracy.
- the system includes m ⁇ n pieces of the optical filters where m represents the number of the optical filters corresponding to each one of the sensor sections and is an integer of three or more, and n represents the number of the sensor sections included in one optical fiber and is an integer of two or more, and the m ⁇ n pieces of the optical filters are configured as a single arrayed waveguide grating (AWG) filter module including m ⁇ n channels or more.
- AWG arrayed waveguide grating
- one optical fiber having a plurality of optical fiber sensors is connected to an arrayed waveguide grating type optical filter module, and necessary optical filters can be equipped.
- the system configuration can be miniaturized and simplified even if many optical filters are necessary.
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Abstract
Description
Consequently, when a vibration propagates to the
Claims (20)
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Application Number | Priority Date | Filing Date | Title |
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JP2006326013A JP5008182B2 (en) | 2006-12-01 | 2006-12-01 | Impact detection system |
JP2006-326013 | 2006-12-01 |
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US20080128600A1 US20080128600A1 (en) | 2008-06-05 |
US7696471B2 true US7696471B2 (en) | 2010-04-13 |
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US11/987,533 Active US7696471B2 (en) | 2006-12-01 | 2007-11-30 | Impact detection system using an optical fiber sensor |
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Also Published As
Publication number | Publication date |
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EP1927839B1 (en) | 2012-10-24 |
JP5008182B2 (en) | 2012-08-22 |
EP1927839A2 (en) | 2008-06-04 |
JP2008139171A (en) | 2008-06-19 |
EP1927839A3 (en) | 2009-05-27 |
US20080128600A1 (en) | 2008-06-05 |
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